There are known prior-art cannulas for blood return to patient's circulation system through the aorta (cf. a catalogue of Aortic Arch Cannula by Sarns Co), consisting of transparent tubes rigidly connected to a head which is in fact a straight or curved radially form, and is essentially another tube but having a smaller bore diameter than the blood supply tube. A stop restricting the depth of the cannula insertion into the aortic incision, is provided at the place where the blood supply tube is joined with the head. The head front end has a bevel edge to facilitate insertion of the cannula into the aortal incision. However, the construction of the cannula involved, whose head is tubular in shape fails to rule out traumatic lesion inflicted upon the aortic tissues during insertion of the cannula into the aortic incision and causes additional loss of blood. In addition, the aforedescribed annula construction makes it impossible to hermetically seal the cannula in order to evacuate air from its interior before being inserted into patient's aorta, which might result in air bubbles penetrating into the aorta.
The disadvantages mentioned above are partly obviated in a venous catheter (cf. a catalogue of Venous Catheter by Sarns Co) used for blood sucking out of the venae cavae and the cardiac atrium of a patient. The venous catheter comprises an elastic transparent tube rigidly coupled to a cone-shaped head which facilitates its insertion into the vessel. Through holes are provided on the head lateral surfaces for passing the blood sucked out of the patient's venae cavae and the cardiac atrium during extracorporeal circulation.
The venous catheter of the construction described above cannot be applied for blood return to patient's aorta, since the head having only lateral holes causes turbulence of the blood flow supplied by the `heart-lung` apparatus. Besides, the construction of such a catheter having the head with through lateral holes, is not air-tight so that there is a risk of air bubbles penetrating into patient's aorta.